package com.wzz.common.rsa;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.UnsupportedEncodingException;

public class Base64 {
  private static final byte[] encodingTable = { (byte) 'A', (byte) 'B', (byte) 'C', (byte) 'D', (byte) 'E', (byte) 'F',
      (byte) 'G', (byte) 'H', (byte) 'I', (byte) 'J', (byte) 'K', (byte) 'L', (byte) 'M', (byte) 'N', (byte) 'O',
      (byte) 'P', (byte) 'Q', (byte) 'R', (byte) 'S', (byte) 'T', (byte) 'U', (byte) 'V', (byte) 'W', (byte) 'X',
      (byte) 'Y', (byte) 'Z', (byte) 'a', (byte) 'b', (byte) 'c', (byte) 'd', (byte) 'e', (byte) 'f', (byte) 'g',
      (byte) 'h', (byte) 'i', (byte) 'j', (byte) 'k', (byte) 'l', (byte) 'm', (byte) 'n', (byte) 'o', (byte) 'p',
      (byte) 'q', (byte) 'r', (byte) 's', (byte) 't', (byte) 'u', (byte) 'v', (byte) 'w', (byte) 'x', (byte) 'y',
      (byte) 'z', (byte) '0', (byte) '1', (byte) '2', (byte) '3', (byte) '4', (byte) '5', (byte) '6', (byte) '7',
      (byte) '8', (byte) '9', (byte) '+', (byte) '/' };

  /**
   * encode the input stream and write the base64 encoded output into the output
   * stream
   * 
   * @throws IOException
   *           if the input/output streams cannot be read/written
   * 
   */
  public static void encode(InputStream is, OutputStream os, int breakLen, String breakStr) throws IOException {

    // The BUF SIZE must be a multiple of 3 to avoid b64 intermeditate
    // padding
    int BUF_SIZE = 16380;
    byte buf[] = new byte[BUF_SIZE];
    int size = is.read(buf);
    int col = 0;
    while (size > 0) {
      // Encode this chunk
      byte encoded[];
      if (size != BUF_SIZE) {
        byte tmp[] = new byte[size];
        System.arraycopy(buf, 0, tmp, 0, size);
        encoded = encode(tmp);
      } else {
        encoded = encode(buf);
      }
      // Now print it to the OS, breaking if required
      for (int i = 0; i < encoded.length; ++i) {
        os.write((char) encoded[i]);
        col++;
        if (col == breakLen - breakStr.length()) {
          os.write(breakStr.getBytes());
          col = 0;
        }
      }
      size = is.read(buf);
    }
  }

  /**
   * encode the input data producong a base 64 encoded byte array.
   * 
   * @return a byte array containing the base 64 encoded data.
   */
  public static byte[] encode(byte[] data) {
    byte[] bytes;

    int modulus = data.length % 3;
    if (modulus == 0) {
      bytes = new byte[4 * data.length / 3];
    } else {
      bytes = new byte[4 * ((data.length / 3) + 1)];
    }

    int dataLength = (data.length - modulus);
    int a1, a2, a3;
    for (int i = 0, j = 0; i < dataLength; i += 3, j += 4) {
      a1 = data[i] & 0xff;
      a2 = data[i + 1] & 0xff;
      a3 = data[i + 2] & 0xff;

      bytes[j] = encodingTable[(a1 >>> 2) & 0x3f];
      bytes[j + 1] = encodingTable[((a1 << 4) | (a2 >>> 4)) & 0x3f];
      bytes[j + 2] = encodingTable[((a2 << 2) | (a3 >>> 6)) & 0x3f];
      bytes[j + 3] = encodingTable[a3 & 0x3f];
    }

    /*
     * process the tail end.
     */
    int b1, b2, b3;
    int d1, d2;

    switch (modulus) {
      case 0: /* nothing left to do */
        break;
      case 1:
        d1 = data[data.length - 1] & 0xff;
        b1 = (d1 >>> 2) & 0x3f;
        b2 = (d1 << 4) & 0x3f;

        bytes[bytes.length - 4] = encodingTable[b1];
        bytes[bytes.length - 3] = encodingTable[b2];
        bytes[bytes.length - 2] = (byte) '=';
        bytes[bytes.length - 1] = (byte) '=';
        break;
      case 2:
        d1 = data[data.length - 2] & 0xff;
        d2 = data[data.length - 1] & 0xff;

        b1 = (d1 >>> 2) & 0x3f;
        b2 = ((d1 << 4) | (d2 >>> 4)) & 0x3f;
        b3 = (d2 << 2) & 0x3f;

        bytes[bytes.length - 4] = encodingTable[b1];
        bytes[bytes.length - 3] = encodingTable[b2];
        bytes[bytes.length - 2] = encodingTable[b3];
        bytes[bytes.length - 1] = (byte) '=';
        break;
    }

    return bytes;
  }

  public static String encodeString(byte[] data, String charset) throws UnsupportedEncodingException {
    return new String(Base64.encode(data), charset);

  }

  public static String encodeString(byte[] data) throws UnsupportedEncodingException{
    return encodeString(data, "UTF-8");
  }

  /*
   * set up the decoding table.
   */
  private static final byte[] decodingTable;

  static {
    decodingTable = new byte[128];

    for (int i = 0; i < 128; i++) {
      decodingTable[i] = (byte) -1;
    }

    for (int i = 'A'; i <= 'Z'; i++) {
      decodingTable[i] = (byte) (i - 'A');
    }

    for (int i = 'a'; i <= 'z'; i++) {
      decodingTable[i] = (byte) (i - 'a' + 26);
    }

    for (int i = '0'; i <= '9'; i++) {
      decodingTable[i] = (byte) (i - '0' + 52);
    }

    decodingTable['+'] = 62;
    decodingTable['/'] = 63;
  }

  /**
   * decode the base 64 encoded input data.
   * 
   * @return a byte array representing the decoded data.
   */
  public static byte[] decode(byte[] data) {

    byte[] bytes;
    byte b1, b2, b3, b4;

    data = discardNonBase64Bytes(data);

    if (data[data.length - 2] == '=') {
      bytes = new byte[(((data.length / 4) - 1) * 3) + 1];
    } else if (data[data.length - 1] == '=') {
      bytes = new byte[(((data.length / 4) - 1) * 3) + 2];
    } else {
      bytes = new byte[((data.length / 4) * 3)];
    }

    for (int i = 0, j = 0; i < data.length - 4; i += 4, j += 3) {
      b1 = decodingTable[data[i]];
      b2 = decodingTable[data[i + 1]];
      b3 = decodingTable[data[i + 2]];
      b4 = decodingTable[data[i + 3]];

      bytes[j] = (byte) ((b1 << 2) | (b2 >> 4));
      bytes[j + 1] = (byte) ((b2 << 4) | (b3 >> 2));
      bytes[j + 2] = (byte) ((b3 << 6) | b4);
    }

    if (data[data.length - 2] == '=') {
      b1 = decodingTable[data[data.length - 4]];
      b2 = decodingTable[data[data.length - 3]];

      bytes[bytes.length - 1] = (byte) ((b1 << 2) | (b2 >> 4));
    } else if (data[data.length - 1] == '=') {
      b1 = decodingTable[data[data.length - 4]];
      b2 = decodingTable[data[data.length - 3]];
      b3 = decodingTable[data[data.length - 2]];

      bytes[bytes.length - 2] = (byte) ((b1 << 2) | (b2 >> 4));
      bytes[bytes.length - 1] = (byte) ((b2 << 4) | (b3 >> 2));
    } else {
      b1 = decodingTable[data[data.length - 4]];
      b2 = decodingTable[data[data.length - 3]];
      b3 = decodingTable[data[data.length - 2]];
      b4 = decodingTable[data[data.length - 1]];

      bytes[bytes.length - 3] = (byte) ((b1 << 2) | (b2 >> 4));
      bytes[bytes.length - 2] = (byte) ((b2 << 4) | (b3 >> 2));
      bytes[bytes.length - 1] = (byte) ((b3 << 6) | b4);
    }

    return bytes;
  }

  /**
   * decode the base 64 encoded String data.
   * 
   * TODO: Use the byte version to avoid duplication?
   * 
   * @return a byte array representing the decoded data.
   */
  public static byte[] decode(String data) {
    byte[] bytes;
    byte b1, b2, b3, b4;

    data = discardNonBase64Chars(data);

    if (data.charAt(data.length() - 2) == '=') {
      bytes = new byte[(((data.length() / 4) - 1) * 3) + 1];
    } else if (data.charAt(data.length() - 1) == '=') {
      bytes = new byte[(((data.length() / 4) - 1) * 3) + 2];
    } else {
      bytes = new byte[((data.length() / 4) * 3)];
    }

    for (int i = 0, j = 0; i < data.length() - 4; i += 4, j += 3) {
      b1 = decodingTable[data.charAt(i)];
      b2 = decodingTable[data.charAt(i + 1)];
      b3 = decodingTable[data.charAt(i + 2)];
      b4 = decodingTable[data.charAt(i + 3)];

      bytes[j] = (byte) ((b1 << 2) | (b2 >> 4));
      bytes[j + 1] = (byte) ((b2 << 4) | (b3 >> 2));
      bytes[j + 2] = (byte) ((b3 << 6) | b4);
    }

    if (data.charAt(data.length() - 2) == '=') {
      b1 = decodingTable[data.charAt(data.length() - 4)];
      b2 = decodingTable[data.charAt(data.length() - 3)];

      bytes[bytes.length - 1] = (byte) ((b1 << 2) | (b2 >> 4));
    } else if (data.charAt(data.length() - 1) == '=') {
      b1 = decodingTable[data.charAt(data.length() - 4)];
      b2 = decodingTable[data.charAt(data.length() - 3)];
      b3 = decodingTable[data.charAt(data.length() - 2)];

      bytes[bytes.length - 2] = (byte) ((b1 << 2) | (b2 >> 4));
      bytes[bytes.length - 1] = (byte) ((b2 << 4) | (b3 >> 2));
    } else {
      b1 = decodingTable[data.charAt(data.length() - 4)];
      b2 = decodingTable[data.charAt(data.length() - 3)];
      b3 = decodingTable[data.charAt(data.length() - 2)];
      b4 = decodingTable[data.charAt(data.length() - 1)];

      bytes[bytes.length - 3] = (byte) ((b1 << 2) | (b2 >> 4));
      bytes[bytes.length - 2] = (byte) ((b2 << 4) | (b3 >> 2));
      bytes[bytes.length - 1] = (byte) ((b3 << 6) | b4);
    }

    return bytes;
  }

  /**
   * Decode the string and convert back the decoded value into a string using
   * the specified charset. Use default encoding if charset is null or invalid.
   */
  public static String decode(String data, String charset) {
    if (charset == null) {
      // use default
      return new String(Base64.decode(data));
    }

    try {
      return new String(Base64.decode(data), charset);

    } catch (UnsupportedEncodingException ex) {
      return new String(Base64.decode(data));
    }
  }

  /**
   * Decode the string and convert back the decoded value into a string using
   * the specified charset. Use default encoding if charset is null or invalid.
   */
  public static String decode(byte[] data, String charset) {
    if (charset == null) {
      // use default
      return new String(Base64.decode(data));
    }

    try {
      return new String(Base64.decode(data), charset);

    } catch (UnsupportedEncodingException ex) {
      return new String(Base64.decode(data));
    }
  }

  /**
   * Compute the base64 encoded size for a stream whose size is specified in the
   * incoming parameter
   * 
   * @param size
   *          the original size (>=0)
   * @return the size of the encoded data
   */
  public static int computeEncodedSize(int size) {
    int encodedSize;
    int modulus = (int) (size % 3);
    if (modulus == 0) {
      encodedSize = (int) (4 * size / 3);
    } else {
      encodedSize = (int) (4 * ((size / 3) + 1));
    }
    return encodedSize;
  }

  // --------------------------------------------------------- Private Methods

  /**
   * Discards any characters outside of the base64 alphabet (see page 25 of RFC
   * 2045) "Any characters outside of the base64 alphabet are to be ignored in
   * base64 encoded data."
   * 
   * @param data
   *          the base64 encoded data
   * @return the data, less non-base64 characters.
   */
  private static byte[] discardNonBase64Bytes(byte[] data) {
    byte temp[] = new byte[data.length];
    int bytesCopied = 0;

    for (int i = 0; i < data.length; i++) {
      if (isValidBase64Byte(data[i])) {
        temp[bytesCopied++] = data[i];
      }
    }

    byte newData[] = new byte[bytesCopied];

    System.arraycopy(temp, 0, newData, 0, bytesCopied);

    return newData;
  }

  /**
   * Discards any characters outside of the base64 alphabet (see page 25 of RFC
   * 2045) "Any characters outside of the base64 alphabet are to be ignored in
   * base64 encoded data."
   * 
   * @param data
   *          the base64 encoded data
   * @return the data, less non-base64 characters.
   */
  private static String discardNonBase64Chars(String data) {

    StringBuffer sb = new StringBuffer();

    int length = data.length();

    for (int i = 0; i < length; i++) {
      if (isValidBase64Byte((byte) (data.charAt(i)))) {
        sb.append(data.charAt(i));
      }
    }

    return sb.toString();
  }

  /**
   * Checks is the given byte is in base64 alphabet
   * 
   * @param b
   *          the byte to check
   * @return boolean true if the byte is in base64 alphabet
   */
  private static boolean isValidBase64Byte(byte b) {
    if (b == '=') {
      return true;
    } else if (b < 0 || b >= 128) {
      return false;
    } else if (decodingTable[b] == -1) {
      return false;
    }
    return true;
  }
}
